Aqueous synthesis of Zn-based ternary core/shell quantum dots with excellent stability and biocompatibility against different cell lines

Ternary quantum dots (QDs) such as zinc indium sulphide (ZIS), copper indium sulphide (CIS) and silver indium sulphide (AIS) have received great attention. Among these ternary semiconductors, the inherent lamellar structure of ZIS makes it difficult to produce zero-dimensional QD material. In addressing this issue, we report the synthesis of ZIS/ZnSe core/shell QDs, for the first time, with enhanced fluorescence and stability. The ZIS QDs were synthesized using thioglycolic acid (TGA) and gelatin as stabilizer and capping ligands. The molar ratio of Zn:Se precursors was varied to obtain enhanced fluorescence. The as-synthesized novel ZIS/ZnSe QDs exhibit narrow emission width and growth of ZnSe shell over ZIS QDs did not result in blue-shifted emission which is a common challenge in AIS- and CIS-based QDs. The as-synthesized QDs are spherical with an average diameter of 6.7 nm and exhibits hexagonal crystal structure. Surface analysis demonstrated that ZIS QDs was stabilized by both gelatin and TGA, while ZIS/ZnSe QDs was only stabilized by gelatin as the growth of ZnSe shell displaced TGA. The cytotoxcity results revealed that QDs maintained excellent biocompatibility towards BHK21-normal fibroblast cells, A549- lung cancer and Hek293-kidney cancer cell lines indicating the potential of the material for biological applications.